The Ohio Valley Node (OVN) joined NIDA's Clinical Trials Network (CTN) four years ago, as one of the CTN's second wave of grantees. From the very beginning, the OVN has been a highly effective, enthusiastic, and energetic node that has excelled in providing scientific and administrative leadership, in collaborating with other nodes and with NIDA staff, and in disseminating information about evidence-based practice and the results of CTN studies. Moreover, the OVN has developed a model bi-directional relationship between its University of Cincinnati-affiliated Regional Research and Training Center (RRTC) and its six original ("core") community treatment programs (CTPs), which are located in Ohio, Indiana, Kentucky, and West Virginia. In this continuation application, the OVN proposes to enhance the geographical and cultural diversity of the CTN by expanding the OVN's Midwestern and Appalachian presence in the network and adding a Mississippi Delta component, via nine additional "protocol-specific" CTPs in five additional states. The fifteen OVN CTPs, which together treat more than 52,000 patients a year, will contribute significantly to the number and variety of potential participants for CTN studies. Each of the core OVN CTPs has participated in at least one CTN clinical trial and two survey studies and all six will continue to share in the administration of the node and in its development of research concepts and protocols. Although the new protocol-specific CTPs will play a more limited role, they are looking forward with enthusiasm to participating in appropriate clinical trials, providing an expanded and enriched patient population to the CTN. During the OVN's first four years in the CTN, we have immersed ourselves fully in all of its activities. We have submitted nine protocol concepts, of which five were chosen for further development;two have been converted into full protocols, including one which is currently enrolling participants. We have been active in the national committees of the CTN, providing five committee chairs and authoring or contributing to many SOPs and "guidance" documents. Unique contributions by the OVN include a system used CTN-wide for monitoring and reporting on staff training requirements and accomplishments, a system for tracking the progress of CTN clinical trials, and a template used to standardize the organization of CTN node budgets. The sense of satisfaction we feel in these and other accomplishments, together with the urgency we feel to continue working on the important search for effective treatments for substance abuse, make us eager to continue the work we have begun.